1. Field of the Invention
This invention relates to an imaging apparatus with its dynamic range expanded, a video camera including the same, and a method of generating a dynamic range expanded video signal.
2. Description of the Prior Art
An imaging apparatus for generating a dynamic range expanded video signal by combining video signals generated substantially at the same time with different exposure intervals is known. Such an image apparatus is disclosed in Japanese patent application provisional publication No. 07131718A. A video signal processing circuit including an edge enhancement signal generation circuit generating an edge enhancement signal from a video signal and a gamma correction circuit for compensating a gamma of the video signal, wherein the edge enhancement signal is not subjected the gamma correction and is added to the gamma-corrected video signal is known. Such a video signal processing circuit is disclosed in Japanese patent application provisional publication No. 63-209373.
The aim of the present invention is to provide a superior imaging apparatus with dynamic range expanded, a superior video camera including the same, and a superior method of generating a dynamic range expanded video signal.
According to the present invention, a first imaging apparatus is provided, which comprises: an imager including driving circuit for receiving an optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second effective detection ranges which are different but continuous; a synchronizing circuit for synchronizing the first video signal with the second video signal every corresponding frames of the first and second video signals; an exposure interval ratio detection circuit responsive to the driving circuit for detecting an exposure ratio between the first and second exposure intervals; a gain adjusting circuit responsive to the first and second video signals from the synchronizing circuit for adjusting a difference between gains of the first and second video signals from the synchronizing circuit in accordance with the exposure ratio from the exposure interval ratio detection circuit for linearity; a mixing control signal generation circuit for generating a mixing control signal indicative of a mixing ratio of the first and second video signals in accordance with the first and second video signals from the gain adjusting circuit; and a combining circuit for generating and outputting a combined video signal from the first and second video signals from the gain adjusting circuit in accordance with the mixing control signal and levels of the first and second video signals to have an expanded detection range such that the first effective detection range is connected to the second effective detection range.
In the first imaging apparatus, the gain adjusting circuit adjusts the difference between gains of the first and second video signals from the synchronizing circuit to provide a linearity in the expanded detection range.
The first imaging apparatus may further comprise: an edge enhancement signal generation circuit for generating an edge enhancement signal from the combined video signal; an edge enhancement amount control circuit for controlling an amount of the edge enhancement signal in accordance with the mixing control signal; and an adding circuit for adding the edge enhancement signal from the gain adjusting circuit and the combined video signal and outputting an edge-enhanced video signal. In this case, the edge enhancement amount control circuit controls the amount of the edge enhancement signal in accordance with the exposure ratio in addition to the mixing control signal.
The first imaging apparatus may further comprise: an edge enhancement signal generation circuit for generating an edge enhancement signal from the combined video signal; a coring amount control signal generation circuit for generating a coring amount control signal in accordance with the mixing control signal; and a coring circuit for effecting a coring operation to the edge enhanced signal in accordance with the coring amount control signal from the coring amount control signal generation circuit; and an adding circuit for adding the edge enhancement signal from the edge enhancement signal generation circuit and the combined video signal and outputting an edge-enhanced video signal. In this case, the coring amount control signal generation circuit generates the coring amount control signal in accordance with the exposure ratio in addition to the mixing control signal.
According to the present invention, a first method of generating a combined video signal from an optical image is provided which comprises the steps of: receiving the optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second effective detection ranges which are different but continuous; synchronizing the first video signal with the second video signal every corresponding frames of the first and second video signals; detecting an exposure ratio between the first and second exposure intervals; adjusting a difference in gains of the synchronized first and second video signal in accordance with the exposure ratio; generating a mixing control signal indicative of a mixing ratio of the first and second video signals in accordance with the gain-adjusted first and second video signals; and generating and outputting the combined video signal from the gain-adjusted first and second video signals in accordance with the mixing control signal and levels of the gain-adjusted first and second video signals to have an expanded dynamic range such that the first effective detection range is connected to the second effective detection range.
According to the present invention, a second imaging apparatus is provided which comprises: an imager including a driving circuit for receiving an optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second dynamic ranges which are different but continuous; a synchronizing circuit for synchronizing the first video signal with the second video signal every corresponding frames of the first and second video signals; a mixing control signal generation circuit for generating a mixing control signal indicative of a mixing ratio of the first and second video signals; a video signal generation circuit for generating a combined video signal from the first and second video signals from the synchronizing circuit in accordance with the mixing control signal and levels of the first and second video signals to have an expanded dynamic range such that the first effective detection range is connected to the second effective detection range; an edge enhancement signal generation circuit for generating an edge enhancement signal from the combined video signal; an edge enhancement amount control circuit responsive to the driving circuit for controlling an amount of the edge enhancement signal in accordance with the mixing control signal; and an adding circuit for adding the edge enhancement signal from the gain adjusting circuit and the combined video signal and outputting an edge-enhanced video signal.
The second imaging apparatus may further comprise a generation circuit generating a coring amount control signal in accordance with the mixing control signal and a coring circuit for effecting a coring operation to the edge enhancement signal in accordance with the coring amount control signal.
According to the present invention, a second method of generating a combined video signal from an optical image is provided which comprises the steps of: receiving the optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second effective detection ranges which are different but continuous; synchronizing the first video signal with the second video signal every corresponding frames of the first and second video signals; generating a mixing control signal indicative of a mixing ratio of the first and second video signals in accordance with the gain-adjusted first and second video signals; generating the combined video signal from the synchronized first and second video signal in accordance with the mixing control signal and levels of the first and second video signals to have an expanded detection range such that the first effective detection range is connected to the second effective detection range; generating an edge enhancement signal from the combined video signal; controlling an amount of the edge enhancement signal in accordance with the mixing control signal; and adding the gain-adjusted edge enhancement signal and the combined video signal and outputting an edge-enhanced video signal.
The second method may further comprise the steps of: generating a coring amount control signal in accordance with the mixing control signal; and effecting a coring operation to the edge enhancement signal in accordance with the coring amount control signal.
According to the present invention, a third imaging apparatus is provided which comprises: an imager including driving circuit for receiving an optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second effective detection ranges which are different but continuous; a synchronizing circuit for synchronizing the first video signal with the second video signal every corresponding frames of the first and second video signals; an exposure ratio detection circuit responsive to the driving circuit for detecting an exposure ratio between the first and second exposure intervals; a mixing control signal generation circuit for generating a mixing control signal indicative of a mixing ratio of the first and second video signals in accordance with the first and second video signals from the synchronizing circuit; a combining circuit for generating a combined video signal from the first and second video signals from the synchronizing circuit in accordance with the mixing control signal and levels of the first and second video signals to have an expanded dynamic range such that the first effective detection range is connected to the second effective detection range; an edge enhancement signal generation circuit for generating an edge enhancement signal from the combined video signal; an edge enhancement amount control circuit for controlling an amount of the edge enhancement control signal in accordance with the mixing control signal and the exposure interval ratio; and an adding circuit for adding the edge enhancement signal from the gain adjusting circuit and the combined video signal and outputting an edge-enhanced video signal.
The third imaging apparatus may further comprise: a coring amount control signal generation circuit for generating a coring amount control signal in accordance with the mixing control signal and the exposure ratio; and a coring circuit for effecting a coring operation to the edge enhanced signal in accordance with the coring amount control signal from the coring amount control signal generation circuit.
According to the present invention, a third method of generating a combined video signal from an optical image is provided which comprises the steps of: receiving the optical image and generating a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second effective detection ranges which are different but continuous; synchronizing the first video signal with the second video signal; detecting an exposure ratio between the first and second exposure intervals; generating a mixing control signal indicative of a mixing ratio of the synchronized first and second video signals in accordance with the synchronized first and second video signals; generating the combined video signal from the synchronized first and second video signals in accordance with the mixing control signal and levels of the first and second video signals to have an expanded detection range such that the first effective detection range is connected to the second effective detection range; generating an edge enhancement signal from the combined video signal; controlling an amount of the edge enhancement signal in accordance with the mixing control signal and the exposure interval; and adding the gain-adjusted enhancement signal from the gain adjusting circuit and the combined video signal and outputting an edge-enhanced video signal.
The third method may further comprise the steps of: generating a coring amount control signal in accordance with the mixing control signal and the exposure ratio; and effecting a coring operation to the edge enhancement signal in accordance with the coring amount control signal.
According to the present invention, a fourth imaging apparatus is provided which comprises: an imager including driving circuit for receiving separated red, green, and blue optical images and generating first red, first green, and first blue video signals with a first exposure interval and second red, second green, and second blue video signals with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first red, green, and blue video signals respectively having first red, first green, and first blue effective detection ranges which are different from the second red, second green, and blue but continuous; a synchronizing circuit for synchronizing the first red, first green, and first blue video signals with second red, second green, and second blue video signals every corresponding frames of the first red, first green, and first blue video signals and the second red, second green, and second blue video signals, respectively; an exposure interval ratio detection circuit responsive to the driving circuit for detecting an exposure ratio between the first and second exposure intervals; a gain adjusting circuit for respectively adjusting difference between gains of the first red, first green, and first blue video signals and second red, first, and video signals from the synchronizing circuit in accordance with the exposure ratio from the exposure interval ratio detection circuit; a mixing control signal generation circuit for generating red, green, and blue mixing control signals respectively indicating mixing ratios between the first red, first green, and first blue video signals and second red, second green, and second blue video signals in accordance with the first red, first green, and first blue video signals and second red, second green, and second blue video signals; and a combining circuit for generating and outputting combined red, green, and blue video signals from the first red, first green, and first blue video signals and second red, second green, and second blue video signals from the gain adjusting circuit in accordance with the red, green, and blue mixing control signals and levels of the first red, first green, and first blue video signals and second red, second green, and second blue video signals to have expanded red, green, and blue detection ranges such that the first red, first green, and first blue effective detection ranges are connected to the second red, second green, and second blue video signals, respectively.
The fourth imaging apparatus may further comprise: a maximum detection circuit for detecting a maximum level among the combined red, combined green, and combined blue video signals for one frame period; and a non-linear processing circuit responsive to display dynamic range data for generating and outputting red, green, and blue display signals respectively having non-linear characteristics such that the maximum level is made equal to or less than the display dynamic range data when the detected maximum level is larger than the display dynamic range data and outputting the combined red, green, and blue video signal as they are when the detected maximum level is not larger than the display dynamic range data.
According to the present invention, a fourth method of generating a combined video signal from an optical image is provided which comprises the steps of: receiving separated red, green, and blue optical images; generating first red, first green, and first blue video signals with a first exposure interval and second red, second green, and second blue video signals with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first red, first,green, and first blue video signals respectively having first red, first green, and first blue effective detection ranges and the second red, second green, and second blue video signals respectively having second red, second green, and second blue effective detection ranges which are different from the first red, first green, and first blue effective detection ranges but continuous; synchronizing the first red, first green, and first blue video signals with second red, second green, and second blue video signals every corresponding frames of the first red, first green, and first blue video signals and the second red, second green, and second blue video signals, respectively; detecting an exposure ratio between the first and second exposure intervals; adjusting difference between gains of the first red, first green, and first blue video signals and second red, second green, and second blue video signals from the synchronizing circuit in accordance with the exposure ratio; generating red, green, and blue mixing control signals respectively indicating mixing ratios between the first red, first green, and first blue video signals and second red, second green, and second blue video signals; and generating and outputting combined red, green, and blue video signals from the first red, first green, and first blue video signals and second red, second green, and second blue video signals from the gain adjusting circuit in accordance with the red, green, and blue mixing control signals and levels of the first red, first green, and first blue video signals and second red, second green, and second blue video signals to have expanded red, green, and blue detection ranges such that the first red, first green, and first blue effective detection ranges are connected to the second red, second green, and second blue video signals, respectively.
The fourth method may further comprise the steps of: detecting a maximum level among the combined red, combined green, and combined blue video signals for one frame period; and generating and outputting red, green, and blue display signals having non-linear characteristics in accordance with display dynamic data and the maximum level such that the maximum level is made equal to or less than the display dynamic range data when the detected maximum level is larger than the display dynamic range data and outputting the combined red, green, and blue video signal as they are when the detected maximum level is not larger than the display dynamic range data.
According to the present invention, a video camera is provided which comprises: a lens unit; separation unit for separating an optical image beam into separated red, green, and blue optical images; an imaging unit including driving circuit for receiving separated red, green, and blue optical images and generating first red, first green, and first blue video signals with a first exposure interval and second red, second green, and second blue video signals with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first red, first green, and first blue video signals respectively having first red, first green, and first blue effective detection ranges, the second red, second green, and second blue video signals respectively having second red, second green, and second blue effective detection ranges which are different from first red, first green, and first blue effective detection ranges respectively but continuous; a synchronizing circuit for synchronizing the first red, first green, and first blue video signals with second red, second green, and second blue video signals every corresponding frames of the first red, first green, and first blue video signals and the second red, second green, and second blue video signals, respectively; an exposure interval ratio detection circuit responsive to the driving circuit for detecting an exposure ratio between the first and second exposure intervals; a gain adjusting circuit for respectively adjusting difference between gains of the first red, first green, and first blue video signals and second red, first, and video signals from the synchronizing circuit in accordance with the exposure ratio from the exposure interval ratio detection circuit; a mixing control signal generation circuit for generating red, green, and blue mixing control signals respectively indicating mixing ratios between the first red, first green, and first blue video signals and second red, second green, and second blue video signals; and a combining circuit for generating and outputting combined red, green, and blue video signals from the first red, first green, and first blue video signals and second red, second green, and second blue video signals from the gain adjusting circuit in accordance with the red, green and blue mixing control signals and levels of the first red, first green, and first blue video signals and second red, second green, and second blue video signals to have expanded red, green, and blue detection ranges such that the first red, first green, and first blue effective detection ranges are connected to the second red, second green, and second blue video signals, respectively.
The camera may further comprise: a maximum detection circuit for detecting a maximum level among the combined red, combined green, and combined blue video signals for one frame period; and a non-linear processing circuit responsive to display dynamic range data for generating and outputting red, green, and blue display signals having non-linear characteristics such that the maximum level is made equal to or less than the display dynamic range data when the detected maximum level is larger than the display dynamic range data and outputting the combined red, green, and blue video signal as they are when the detected maximum level is not larger than the display dynamic range data.